Method and apparatus for orientating core sample and plug removed from sidewall of a borehole relative to a well and formations penetrated by the borehole

Abstract

A method and apparatus for determining the location in space of a formation sample is set forth. This involves a tool which is typically run on a wireline in a well, the tool supporting orthogonal positioned magnetometers and similar orthogonal accelerometers for measuring movement of the tool along the well borehole whereby components of the magnetic field and gravity field are measured to enable determination of the well in space. The tool supports an axially positioned centrally located core cutting apparatus and a laterally projecting plug cutting apparatus; scribe marks formed on the formation samples orient the samples relative to the tool and the tool is located in space from the above mentioned measurements so that the position of formation samples can be determined.

What is claimed is: 
     
       1. A method of determining the position in space of a formation sample comprising the steps of: (a) moving sensors from the surface via a wireline cable along a well borehole from the well head to a specified depth in a well wherein the movement along the well is sensed by determining gravity or magnetic field measurements during movement and the gravity or magnetic field measurements are resolved into coordinate components;   (b) from the coordinate components, determining the location of the tool along the well borehole; and   (c) cutting a formation core sample at that location wherein the relative position of the sample with respect to the tool is known so that the location of the tool determined with the measurements as the tool moves along the well borehole provides a description in three variables of the formation sample in space with respect to the well borehole.   
     
     
       2. The method of claim 1 wherein a core sample is cut from the well borehole at the bottom thereof. 
     
     
       3. The method of claim 1 wherein measurements derived from the gravity or magnetic sensors provide an indication of well depth. 
     
     
       4. The method of claim 1 wherein cable length extending from the surface measures the well depth of the tool. 
     
     
       5. The method of claim 1 wherein well depth of the tool is measured by at least two alternate techniques one of which is cable length extending from the surface to provide data for comparison. 
     
     
       6. The method of claim 1 wherein a core is cut from the formation axially extending along the well borehole, and is moved to the surface along the well borehole; a radial plug is cut from the sidewall of the well borehole at a depth to obtain a sample from formations adjacent to the core cut from the formation; and   comparing the radial plug cut from the sidewall to the core to obtain information about the formation from which the plug was cut.   
     
     
       7. The method of claim 6 including the step of determining angular orientation of the plug to the core to position the core relative to the formation from which the plug was cut. 
     
     
       8. The method of claim 6 wherin said plug and core are tested for directional characteristics to obtain a position for the core relative to the formation. 
     
     
       9. The method of claim 6 wherein a similar plug is cut radially from the core, and is compared in directional characteristics to determine the position in space of said core. 
     
     
       10. The method of claim 9 wherein said core is plugged to obtain an oriented plug for comparison with radial plug. 
     
     
       11. The method of claim 10 wherein said oriented plug and said radial plug are tested for paleomagnetic vector direction. 
     
     
       12. The method of claim 11 wherein both of said plugs are obtained at radial lines relative to the axis of the well borehole. 
     
     
       13. The method of claim 12 wherein both of said plugs are measured for angular position relative to a set of three orthogonal coordinate axes. 
     
     
       14. The method of claim 1 wherein acceleration in three orthogonal coordinate axes is measured in a coordinate system defined by gravity on moving sensors along a well borehole. 
     
     
       15. The method of claim 14 wherein three orthogonal magnetic field sensors measure the magnetic field components of the earth along the well borehole. 
     
     
       16. An apparatus for determining the location in a well borehole of a sample obtained from a formation along the well borehole comprising: (a) sample cutting means suspended by a wireline cable in a well borehole and having an elongate housing and including cylindrical sample receiving means; and   (b) gravity sensor means mounted for movement with said housing, said gravity sensor means measuring acceleration movement of said housing as said housing moves along a well borehole from a well head toward the bottom of a well borehole, said sensor means forming a gravity vector signal providing the location of the well borehole in space defined by three orthogonal coordinate dimensions.   
     
     
       17. The method of claim 16 wherein said housing is connected to a flexible cable means including conductors connected from said housing to provide signals at the well head providing the location of the well borehole in space. 
     
     
       18. The apparatus of claim 17 further including three orthogonal sensors for the magnetic field of the earth which sensors form three dimensions in space.